The overall objectives of the proposed research is to gain insight into the normal and abnormal development of binocular visual functions in the primate visual system. Binocular vision depends on cortical mechanisms that can efficiently combine neural signals from the two eyes and the normal development of these mechanisms require both the maturation of monocular visual functions and well correlated binocular inputs to the visual cortex. While the central visual pathway is known to exhibit considerable neural plasticity during early development, we know very little about how normal binocular signal interactions develop at the cellular level in the primates or how such development is altered by early abnormal visual experience. The goal of the proposed experiments is to fill this gap. We will conduct extracellular single-unit experiments in the primary visual cortex (V1) of anesthetized and paralyzed rhesus monkeys to determine: 1) how signals from the two eyes are combined in individual neurons and what is the nature of disparity tuning at the critical stages of normal development, and 2) how the normal pattern of binocular interactions is altered in animals reared with selective abnormal visual experience (e.g., strabismus and anisometropia). in both studies, we will focus on the notion of spatial frequency-dependent nature of disparity processing and its developmental alteration (normal or abnormal development). Ongoing psychophysical experiments that will characterize monocular and binocular vision of our experimental subjects will be completed prior to proposed neurophysiological experiments. Thus, it will be possible to directly compare the behavioral and physiological deficits produced by abnormal visual experience in the same animals. The proposed study will provide information on the cortical processes that regulate the maturation of binocular vision in primates including humans, and how these normal processes are influenced by abnormal visual experience. The results from the proposed study will increase our knowledge of the neural deficits underlying many common vision anomalies in humans, and are likely to contribute to the prevention and treatment of binocular vision deficits associated with infantile strabismus, anisometropia, and other early selective visual deprivations.